1. Field of the Invention
The present invention relates to a draw-ironed can composed of a surface-treated steel plate and a process for the preparation thereof. More particularly, the present invention relates to a draw-ironed can in which the amount plated of tin is much smaller than in draw-ironed cans composed of conventional tin-plated steel plates and the lacquer adhesion and corrosion resistance are highly improved, and a process for the preparation of such draw-ironed can.
2. Description of the Prior Art
A can body obtained by subjecting a metal blank to drawing between a punch and a die and then to ironing is advantageous in various points. For example, there is no seam in a barrel portion or in a joint portion connecting the barrel portion to a bottom portion, and the appearance is very good. Furthermore, double seaming of a bottom lid or formation of a seam need not be performed. Moreover, since the thickness of the barrel portion is reduced, the amount used of the metal blank can be reduced. Because of these advantages, these can bodies are widely used for canned drinks and foods.
Metal blanks for draw-ironed cans should possess a good formability. From the viewpoint of the formability, relatively expensive metal blanks such as aluminum plates and tin-plated steel plates (tinplates) are ordinarily used. Tin-plated steel plates involve a problem of exhaustion of tin resources, and the cost of tin is increasing year after year. Therefore, from the economical viewpoint, it is desired that the amount plated of tin should be reduced to a level as low as possible.
However, trials to reduce the amount plated of tin are limited from the viewpoints of the formability and corrosion resistance, because at the step of drawing and ironing a tin-plated steel plate, the tin layer acts as a solid lubricant and to a processed can body, the tin layer acts as a protecting cover layer. Therefore, tinplates #50 to #100 having a plated tin amount of 5.6 to 11.2 g/m.sup.2 are now used as metal blanks to be draw-ironed.